The present invention generally relates to a raised floor system for use in a semiconductor fabrication facility and more particularly, relates to a raised floor system that utilizes transparent view panels constructed by a tempered glass panel supported by an apertured steel panel to allow observation of utility gauges mounted under the raised floor system.
In the recent development of semiconductor fabrication technology, the continuous miniaturization in device fabricated demands more stringent requirements in the fabrication environment and contamination control. When the feature size was in the 2 xcexcm range, a cleanliness class of 100xcx9c1000 (i.e., the number of particles at sizes larger than 0.5 xcexcm per cubic foot) was sufficient. However, when the feature size is reduced to 0.25 xcexcm, a cleanliness class of 0.1 is required. It has been recognized that an inert mini-environment may be the solution to future fabrication technologies when the device size is reduced further. In order to eliminate micro-contamination and to reduce native oxide growth on silicon surfaces, the wafer processing and the loading/unloading procedures of a process tool must be enclosed in an extremely high cleanliness mini-environment that is constantly flushed with ultra-pure nitrogen that contains no oxygen and moisture.
Different approaches in modern clean room design have been pursued in recent years with the advent of the ULSI technology. One is the utilization of a tunnel concept in which a corridor separates the process area from the service area in order to achieve a higher level of air cleanliness. Under the concept, the majority of equipment maintenance functions are conducted in low-classified service areas, while the wafers are handled and processed in more costly high-classified process tunnels. For instance, in a process for 16 M and 64 M DRAM products, the requirement of contamination control in a process environment is so stringent that the control of the enclosure of the process environment for each process tool must be considered. This stringent requirement creates a new mini-environment concept which is shown in FIG. 1. Within the enclosure of the mini-environment of a process tool 10, an extremely high cleanliness class of 0.1 (i.e., the number of particles at sizes larger than 0.1 xcexcm per cubic foot) is maintained, in contrast to a cleanliness class of 1000 for the overall production clean room area 12. In order to maintain the high cleanliness class inside the process tool 10, the loading and unloading sections 14 of the process tool must be handled automatically by an input/output device such as a SMIF (standard mechanical interfaces) apparatus.
FIG. 1 also shows a raised floor system 30. The raised floor system 30 is normally installed between 45 and 60 cm above the finished concrete waffle slab 32. The raised floor system 30 in general, covers the entire clean room production area. The grid 34 of the raised floor is based on a 60xc3x9760 cm system and is normally aligned with the center lines of the filter ceiling grid. Some of the floor tiles 36 are perforated for circulating the clean room air 38. The adjustment of the air pressure in the clean room and the balancing of air flow can be achieved by selecting floor tiles with proper perforations.
In the raised floor system 30 shown in FIG. 1, the floor tiles 36 should be static-dissipative and made of non-combustible material that is also chemical abrasion resistance. A frequently used material is vinyl which is impact resistant and meets the electrostatic discharge isolation resistance requirement for the clean room environment.
A detailed, cross-sectional view of a raised floor system 30 is shown in FIG. 2. The raised floor system 30 should be laterally stable in all directions with or without the presence of the floor tiles 36. This is achieved by anchoring the pedestals 40 into the concrete slab floor 32 and by the further use of stringers 42 and steel braces 44. The floor tiles are supported by the stringers 42 which are in turn supported at each corner by adjustable height pedestals 40. As shown in FIG. 2, the pedestals 40 are bolted to the finished concrete waffle slab 32. An insulation plate 46 placed on top of each pedestal 40 attenuates foot step sound and ensures electrical isolation. The steel braces 44 are used to further increase the rigidity of the raised floor system 30 and the pedestal support.
In recent years, for safety considerations such as for minimizing the risk from earthquake vibration in a highly stacked fab plant, screws or bolts are required at each corner of the raised floor panels 36. This makes it impossible to easily remove the floor panels by just using suction cups and lifting the panels. The structural reinforcement on the raised floor design therefore presents great difficulties in accessing utility panels that are frequently mounted under the raised floor. In order to access the utility panels, the screws or bolts at the corners of the floor panels must first be removed before a suction device can be used to lift up the floor panels. Furthermore, since the floor panels are normally fabricated of a vinyl plastic material that is opaque, the display on the utility panels, i.e., various gauges and dials, cannot be read or accessed without first removing the floor panels.
It is therefore an object of the present invention to provide a raised floor system for a semiconductor clean room facility that does not have the drawbacks or shortcomings of the conventional raised floor systems.
It is another object of the present invention to provide a raised floor system for a semiconductor clean room facility wherein the floor panels can be easily removed for accessing the utility panels.
It is a further object of the present invention to provide a raised floor system for a semiconductor clean room facility wherein the floor panels are not screwed into the stringers underneath.
It is another further object of the present invention to provide a raised floor system for a semiconductor clean room facility that is equipped with transparent panels supported by apertured steel panels.
It is still another object of the present invention to provide a raised floor system for a semiconductor clean room facility that is equipped with transparent panels such that the utility panels mounted thereunder can be observed.
It is yet another object of the present invention to provide a raised floor system for a semiconductor clean room facility that is equipped with removable floor panels each equipped with four view panels.
It is still another further object of the present invention to provide a raised floor system for a semiconductor clean room facility that is equipped with transparent tempered glass panels that are coated with a shatter-proof coating.
It is yet another further object of the present invention to provide a raised floor system for a semiconductor clean room facility that is equipped with transparent tempered glass panels mounted in a floor panel that are anti-electrostatic, highly rigid and scratch resistant.
In accordance with the present invention, a raised floor system for a semiconductor clean room facility can be provided which includes a first multiplicity of pedestals mounted to a floor at a lower end of the pedestals, a second multiplicity of stringers mounted to a top end of the first multiplicity of pedestals such that the stringers are parallel to the concrete floor, a third multiplicity of floor panels mounted to the second multiplicity of stringers, each of the floor panels includes at least one cavity therein adapted for receiving at least one view panel that is substantially transparent and is supported by at least one apertured steel panel in the third multiplicity of floor panels.
The raised floor system for a semiconductor clean room facility may further include a fourth multiplicity of braces for supporting the first multiplicity of pedestals. The at least one cavity in each of the third multiplicity of floor panels may further include a ridge portion along at least two sides in a rectangular shape cavity for supporting a view panel. The at least one cavity in each of the third multiplicity of floor panels may further include a ridge portion along four sides in a rectangular shaped cavity for supporting a view panel. The at least one cavity in each of the third multiplicity of floor panels may have a rectangular shape, or a square shape.
In the raised floor system for a semiconductor clean room facility, the at least one view panel may be formed of a transparent tempered glass panel supported by at least one apertured steel panel. The tempered glass panel may be coated on the backside with a shatter-proof coating. The at least one view panel may include four view panels of equal size. The at least one apertured steel panel may be fabricated of stainless steel. The at least one tempered glass panel may have a thickness of not less than 7 mm, or a thickness between about 7 mm and about 15 mm. The at least one apertured steel panel may have a thickness of at least 3 mm, or a thickness between about 3 mm and about 10 mm. The word xe2x80x9caboutxe2x80x9d used in this writing indicates a range of value that is xc2x110% of the average value given.
The raised floor system for a clean room of a semiconductor fabrication facility may further include a plurality of utility panels mounted under the third multiplicity of floor panels which are visually inspectable through the at least one view panel. The at least one view panel has a top surface substantially flush with a top surface of the third multiplicity of floor panels when mounted in the third multiplicity of floor panels. The at least one view panel may further include two apertures therethrough adapted for opening the view panel by human fingers. The at least one panel insert may be fabricated of a material that is anti-electrostatic and abrasion resistant.